I have a straight question:

If I install a K&N filter in the standard airbox with the lid still on and then rejet without replacing the stock exhaust will the effort be worth it?

Has anyone done this and can they advise before is take the carb apart only to find it was a waste of time!

 

Yah, I think it is pretty much a waste of time. BUT, if you take the airbox lid off, I dont' think it is.

 

Kit arrived today so looks like I'll have to install the K&N and fit the jets and then report back for anyone else considering this mod now or in the future.

 

Brocksz have you tried this or is it just what you think?

Don't really wnat to mess with the standard carb setting (mixture) if it will not improve the performance.

I need someone to reply who has 'been there and done it' without an aftermarket exhaust.

 

Yes, I'm running a UNI filter, k&n jet kit, with no airbox lid right now. I also removed my spark arrester. Its not that big of a project, it only took about 45min. Be real careful when you remove the bowl from the bottom of the carb. though, they put so much damn lock tight on those screws there a pain in the a$$ to get off. Also go get some allen head screws to replace the regular phillips head screws.

 

Ok, so being honest is it worth the hassle of replacing the jets etc if your not replacing the exhaust or taking the airbox lid off? Is there a performance increase or not. Your advice would be much appreciated buddy as it could save me a lot of aggro. I have no intention of replacing the exhaust. Do I do it or not?

 

Like I said before, if you leave your airbox lid on, I don't think it's worth it. But, if you take your airbox lid off, I think it IS worth it.

 

Think of a motor as a complete package. Power comes from air, not fuel. So to increase power, the whole system needs to breath better. It was designed to work together...so when stock, the air fliter and assorted hardware( tubes and boxes and lids) and the exhaust ( diameter and length) are balanced, and the jetting is correct. Now if you improve the intake, and not the exhaust...there may be a tiny increase in power, but only you can determine if its worth the money spent. Most lkely itll run a bit leaner, and the jetting will correct that.
Sounds like you want the air box lid on, and the exhaust left stock...if so, youre not gonna get much power increase. On a 250cc motor, you might gain 1/3 hp.

 

nicks3,
I have a stock 05 z400 and am still waiting to do some mods, but my roomate with an 04 z400 put on the K&N and instead of buying a new exhaust, he opened the end and cut out the piece at the end of the pipe. I dont know the name of the piece, but it was a smaller tube restricting airflow. After doing this he did rejet, bc he basically had to, and the bike runs really well. I know an aftermarket pipe would be better, but for a cheap mod the bikes response is better and it has a nice, deeper sound than stock. I dont know if the rejet is necessary after just the new K&N, but going a little farther and taking the piece out of the pipe will help out. Just my 2 cents. let us know where it gets you.

 

Thanks for the information it is all appreciated. From what has been said, which makes a lot of sense, I dont think there will be much gain and if that is the case then I dont see the point in messing with the standard settings. Think I'll just put the K@N in when its due for a service and leave it at that.